Topochemical Photopolymerization above the Bulk Melting Temperature in Noncovalent Monolayers on Graphite

Abstract While studies of surface‐templated topochemical reactions often focus on the central role of monomer ordering, the reactions themselves frequently require Ångström‐scale dynamics to form new bonds. Here, it is showed that elevated temperatures increase the topochemical reaction efficiency of 10,12‐tricosadiynoic acid (TCDA), a widely utilized commercial diacetylene monomer, assembled on highly oriented graphite (HOPG) substrates. Up to ≈45 °C, Arrhenius temperature dependence is observed for the reaction, with E _a = 5.9 kcal mol ⁻¹ (0.26 eV), consistent with limitations imposed by the propagation step of the reaction, which requires monomer dynamics within the lattice. At higher temperatures, t _0.5 does not continue to decrease. However, the number average degree of polymerization continues to increase, from 97 at 5 °C to 248 at 65 °C, and the number density of polymers formed per incident photon increases by 6–13‐fold at elevated temperatures (45–65 °C) in comparison with polymerization at 5 °C. Together, these changes in the on‐surface reaction greatly increase molecular sheet integrity, resulting in a 10‐fold increase in the efficiency of a covalent mesh‐forming reaction that transfers TCDA sheets to soft polydimethylsiloxane.